In the present day, ion implanters are often constructed to optimize implantation according to a specific set of applications. In current applications, for example, some beamline ion implanters are configured to generate high current ribbon beams in which the beam cross section that intercepts a substrate is defined by a beam width that is much greater than the beam height. In some configurations the beam width is slightly larger than the size of a substrate at the substrate plane e.g., 200, 300, or 400 mm, while the beam height is on the order of 10 mm, 20 mm, or 30 mm. By scanning the substrate with respect to the ribbon beam in the direction of the beam height, the entire substrate may be implanted by the ion beam. Various components of the beamline of a high current ribbon beam ion implanter are set to tailor operation for a ribbon beam, including ion source, scanning components, focusing components, and collimation components. In this manner, high current ion implantation of a substrate can be optimized using a ribbon beam ion implanter.
For other ion implantation applications, it may be preferable to use a spot beam ion beam in which the beam height and beam width are more equal. In many applications the beam height of a spot beam is the same size or somewhat larger than the beam width, and may be on the order of 20 to 30 mm. One advantage afforded by spot beam ion implantation is the better control of dose uniformity afforded by spot beams. In a spot beam ion implantation application, the spot beam may be scanned along a first direction to cover the dimension of a substrate in that direction that is being implanted. At the same time, the substrate may be scanned in a direction perpendicular to that of the scan direction of the spot beam. The local ion dose concentration can be modified by adjusting the speed of the ion beam along the direction of spot beam scanning. This can be accomplished under computer control in a manner that allows the spot beam scanning to be carefully controlled to optimize ion dose uniformity. Often, such spot beam ion implantation does not generate as high a dose rate of ions to the substrate in comparison to ribbon beam ion implantation.
Accordingly, it is common practice for a ribbon beam ion implanter to be employed for certain ion implantation steps or for certain substrates, such as high dose implantation, while a spot beam ion implanter is employed for other ion implantation steps that require better dose control. It is with respect to these and other considerations that the present improvements have been needed.